Calculating instrument.



W. W. CRAIG.

CALCULATING INSTRUMENT. APPLICATION FILED AUG. 2 1911.

1,048,044. Patented D6G.24,1912.

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' I Fla. 3; 22 m1 mf/iessas //7re/7/0/" UNITED STATES. PATENT OFFICE.

WILLIAM WALLACE CRAIG, OF CHATHAM, NEW BRUNSWICK, CANADA.

CALCULATING INSTRUMENT.

Specification of Letters Patent.

' Application filed August 21, 1911; serial No. 645,174.

Patented Dec. 24, 1912.

. lowing is a full, clear, and exact description.

This invention relates to improvements in I calculating instruments and the object is to rovide a simple device for calculating and Indicating the variouslines and angles reuired by sheet metal workers in designing t e various parts of pipe offsets, fru'stoconical containers and the like.

The instrument is designed to supplement or replace that part of geometrical designing known as plan and elevation drawing, as applied to general sheet metal'work, and at the same time provide a convenient means of calculating lines and areas.

The device consists of a plate, preferably of metal, graduated vertically and horizontally. in inches, and provided at the upper left hand corner with protractor scales. A pin is fixed at this corner on which a suitably graduated scale pivots. A bevel gage and a flexible rule are provided which may also be mounted on the pivot pin.

Referring to the drawings ;Figure 1 is a fragmentary plan view of the graduated late with the ivoted scale in position. ig. 2 is a plan view of the bevel gage. Fig. 3 is a plan view of changing scale accompanying the device. Fig.1 4 is a perspective VIGW'Of a fragment of the flexible rule.

In the drawings, ,5 designates a plate, preferably of metal, graduated horizontally and vertically in inches, as shown at 6 and 7 respectively. These graduation lines extend across the plate and divide the surface into squares, as shown in the drawings. In the upper left hand corner-of the plate, protractor scales 8 and 9 are formed having their centers at the corner or zero point of the graduated surface. Both protractor scales are graduated from 0 to 180,the inner protractor scale 8 beingof the usual form while the outer protractor scale is only 90 actual measurement, each halfde'gree being considered as a whole degree. -A'-pin 10 is fixed to the plate, the axis of this'pin being at 'the exact center of the protractor scales. A bar 11 is provided having at one end a lug 12 through which the pin 10 passes, thus-pivotally mounting the'bar so that it may be swung freely over the graduated surface of the plate 5. The big 12 allows the" pin to be positioned centrally in line with the edge 13 of the bar, so that this edge will always be radial to anyare through which the bar'is swung. The bar 11 is provided with a scale 14, graduated in inches, on the edge 13 and is also provided ,on the bod with two additional scales 15 and 16. T e scale 15 indicates the circumference of circles, the diameters of which are expressed in inches on the scale 14. The scale 16 gives the sides of squares equal in area to circles Whose diameters are expressed in inches on the scale l lwhich readings are obviously the square roots of the areas of the circles. The readings on the scales 15 and 16 represent inches; thus taking one inch as diameter, it will be seen that the corresponding reading on the scale 15 is slightly past the 3% inches graduations,

namely 3% inches. In the same way, the side of a square of equal area is shown on the scale 16 to be sli htly, greater than of an inch. The area o the square may be readily obtained by squaring the measurement.

A bevel gage 17 shownin Fig. 2, is provided with a lug 18 to allow the pivot aperture 19 tobe centrally in line-with edge 20 of thegage. This gage is used onthe upper half of the rotractor scale 8 to ascertain the angle 0 the desired level. g

A flexible rule 21, preferably made of a thin ribbon of spring steel. looped-at one end 22 to engage the pin 10 and hold the rule on edge, is provided I with suitable graduations 23 in inches, and is used to determine the length of irregular lines. v A changing or comparing scale 24; accompanies the instrument, this scale being divided on one edge 25 from tenths to hundredt-hs of an inch, and on the other edge, from sixteenths to sixty-fourths of an: inch, at 26, and into twelfths ofan inch at 27.

This scale is used to change the usual division's into twelfths or into hundredths, when it is desired to calculate in decimals, and t0 give irregular bisections to elevations as in the case of scoops etc.

The use or applicatlon of the device is very simple. To obtain the elevation of a cylinder the diameter is noted on the top scale 6 and the heighten the side-scale 7: The rectangle formed by the graduation lines from these 'pointsiis the required elevation. If the cylinder is a pipe and it is desired to designan offset, the angle of the ofiset is first determined and the rule 11 moved to the graduation for this angle on the outer or miter protractor 9. llhe degrees of this protractor being in reality half degrees, will bisect the angle and give the true miter line. This miter line may be indicated on the plate 5 in any suitable manner. In developing the required curve to form the miter line of cylindrical bodies,

it is customary to divide the circumference (on a plan view) into eight or more parts, transfer these divisions to an elevation having the miter line drawn thereon, and then transfer the intersections of the transfer and miter lines to a development of the cylinder, having parallel lines thereon corresponding to the division points on the circumference. The intersections of the parallels in the development and the second transfer lines, give points on the required curve. This method is tedious and allows great latitude for error. To obtain the eight circumferential divisions transferred to the elevation, the rule 11 is moved to on the protractor 8 and the distance on the rule between the graduation indicating the diameter of the'cylinder and the point of the rules intersection with the adjacent side of the elevation is bisected. A vertical line drawn through this bisection point is one of the required lines. For example, supposing the pipe diameter, the elevation is that part ofthe graduated surface between the scale 7 and the vertical line of the three inch graduation. in the scalev 6. The rule 11 is moved to 45, as shown, and the diameter of the cylinder, 3 inches, is found thereon. The distance from the three inch graduation to the point of the rules intersection with the vertical 3 inch graduation line, is bisected. This intersection is seen on the drawing to be the al inch graduation on the rule. The oint of bisection between 3 and is, thereore, at the 3% graduation, or inch actual measurement. A vertical line drawn on the plate 5 through this point is one of the required eight lines. Measuring inch from 9 on the rule, the position of the corresponding vertical on the left hand is found. The remaining vertical is in the center ofthe elevation, namely the vertical line of the 1%- inch graduation on the scale ti. These verticals are intersected by the -miter line already formed. Allthe measurements may now be read on the instru ment and transferred directl to the metal sheet, from which the pipe is to be made. The development is marked on the sheet as usual. The length of the development for the required diameter isfound on the circumference scale 15, and the required number of parallels markedwhich correspond to the bircnmference divisions. The distance of the intersection of the verticals to be three inches in :nuse of aright angled triangle is equal to with the miter line, from the top of the graduated surface, is indicated by the scale 7, andt'hese distances are laid oil on the metal sheet givingthe points through which the curve for the miter line will pass.

To obtain the proper radius of are for making a cone, take half the diameter of the base on the scale 6, say three inches, and move the rule to the graduation on the vertical 3 inch line indicating the altitude of the cone. The reading on the scale 14 of the rule Where it intersects the vertical line is the requiredradius. When a given length of metal is to be divided into an equal number of parts, the following method will give quick and accurate results.

Supposing the length of the strip to be 5 "inches and the required number of equal divisions to be 4, 7} of 5 is found as follows :Find 4 (the denominator of the fraction)- on the top of the square, then find 1 (the numerator) on vertical line from d.

Hold the rule at this point and find 5 on the top of the square. The measurement on the vertical line from 5 where it is intersected by the rule will be found to be 1%; which is the desired quotient.

The operation above set forth partly explains the arithmetical principles of the device as they may be used in working with fractions and mixed numbers.

" Knowing that the square of the hypotethe combined squares of the base and altitude, and supposing the figures on top of lllll square to represent bases, the vertical lines to represent altitudes and the rule to represent ypotenuses, it will be seen at a glance that this principle will he found very useful as well as very convenient.

A number of other useful geometrical and mathematical calculations may be made with great ease by means of this instrument, but a knowledge of these is not necessary to the complete understanding of the instrument as used for sheet metal work.

While the-device has been shown and dc scribed as divided into inches, it is obvious that it may be divided according to the metric or any other system of measurement.

Having thus described my invention, what I claim is A calculating instrument forsheet metal workers, comprising a plate having its sur--- face graduated vertically and horizontally I whereby the elevation and development of an object will be indicated, a protractor scale centered in one corner of the plate having fractions of degrees marked as whole degrees thereomwhereby the fractions of an angle will-be found at the numeral indicatthe 'whole angle, bar pivoted attl le center ofsaid protractor scale, a scale on said bar arranged'etoindicate on the elevation shown by theplate the position of fiilmfifl ferential divisions, a second scale formed on In witness whereof I have hereunto set my said blar gndicating ghe circumference oficirhand in the presence of two witnesses.

cles t e iameter o w ich is indicate on r the first scale, and a third scale on said bar WILLIAMWALLACE CRAIG indicating the square root of the areas of Witnesses:

circles the diameters of which are indicated Ross HARDING,

on the first scale. DAN DIOKISON. 

